The incidence of peritoneal carcinomatosis and impact on outcomes in relapsed early T4 colorectal cancer.

Abstract

73 Background: There is limited data regarding the association between peritoneal carcinomatosis (PC) and clinical outcomes in colorectal cancer (CRC). We examined the incidence of PC and explored the relationship to survival (RFS & OS) in CRC. Methods: The demographic and clinical details of patients with stage II/III CRC referred to a tertiary centre in Western Sydney between 2009-2016 were obtained. Associations between clinical outcomes and baseline prognostic factors were investigated using proportional hazards regression models. The effect of prognostic factors on outcome were examined by tumour stage. Results: 495 patients were identified, 281 (57%) with stage II and 214 (43%) with stage III. Median follow-up was 38 months. 330 (67%) had T3 and 165 (33%) had T4 disease. Median age at diagnosis was 72 years (19 -94). 104 (21%) patients relapsed, 24 (23%) had PC and of those, 6 had PC as their only site of metastasis. 10% (n = 5) with T3 developed PC compared with 35% (n = 19) with T4 disease (P = 0.02). Compared with non-PC, PC was associated with poorer median OS (28 Vs 46 m; p = 0.03). Median RFS for T3 was 16 months, T4, 14 months (NS). Median OS for T3 was 34 months Vs T4 28 months (P = 0.45). Of those with PC relapse, the diagnosis of PC was highest in the first two years post-operatively (88%). 9 patients (38%) with PC died due to bowel obstruction Vs 4 (5%) patients with non-PC relapse (P < 0.01). Poorer OS was associated with PC (HR 1.74; p = 0.03), right sided primary (HR 1.602; P = 0.05), T4 stage (HR 1.69; P = 0.03), LVI (HR 1.95; p < 0.01), N stage (HR 1.51; P < 0.01), and number of metastases at baseline (HR 1.25; p = 0.04). On multivariable analysis right sided primary and T4 stage remained significant. Conclusions: Patients with PC relapse have an 18 month shorter median OS than those with non-PC relapse. Further, PC recurrence is more common in patients with T4 compared with T3 CRC and was the only site of metastatic disease in 7% of relapsed patients with T4 CRC. Consideration for peritonectomy and/or HIPEC should be given for patients with PC metastases. For patients with resected early stage T4 CRC, consideration should be given for surveillance laparoscopy.